1. Field of the Invention
This invention relates to a printer equipped with a validation paper feeding mechanism, and more particularly to a printer having a standard paper feeding roller and a validation paper feeding roller, which are in contact with a friction roller.
2. Description of the Related Art
A printer for printing not only standard papers, i.e. continuous paper and cut paper, but also validation papers using a single print head is known from, for example, Japanese Patent Laid-Open Publication No. 4-179563(179563/1992). Validation papers are a kind of cut papers composed of a multiplicity of copy sheets which are generally regular in size.
In the printer disclosed in the above Japanese Patent Laid-Open Publication, a platen and a recording paper pressure roller are mounted on a swing arm which is angularly moved by a plunger-type solenoid to bring the platen and the recording paper pressure roller against and apart from the print head and a recording paper drive roller, which are arranged in confronting relationship with the swing arm. A recording paper path defined by the platen and the print head and by the recording paper pressure roller and the recording paper drive roller can be opened and closed. An upper part of the recording paper path serves as a common paper outlet port for the cut paper, continuous paper and validation paper, while a lower part of the recording paper path is divided into a cut paper path and a validation paper path. A continuous paper path communicates with a central portion of the recording paper path between the print head and the recording paper drive roller.
The paper feeding mechanism of this printer comprises the plunger-type solenoid, the swing arm on which the platen and the recording paper pressure roller are mounted, and the record paper drive roller disposed stationary.
For printing a validation paper, the paper is inserted into the recording paper path for validation paper from the paper outlet port at the upper part of recording paper path, with the recording paper path kept open by not energizing the plunger. Then, the plunger is energized to angularly move the arm, bringing the platen mounted on the arm to face the printer head and also bringing the recording paper pressure roller to face the recording paper drive roller. In this state, the print head is activated to perform printing, and the recording paper drive roller is rotated in the paper feed direction to perform paper feed.
With this prior art printer, however, if the validation paper is printed as set in front of the print head when the cut paper is also set in front of the print head, the cut paper is fed together with the validation paper with both papers caught by the recording paper pressure roller and the recording paper drive roller.
Further, since both the platen and the recording paper pressure roller are mounted on the swing arm, the swing arm would be relatively large in size and a large-size plunger-type solenoid is necessary for angular moving the large swing arm. This causes the entire paper feed mechanism larger in size and raises the cost for manufacture because of generally expensive plunger-type solenoid.
There is known another printer having a standard paper feed roller for feeding a standard paper and a validation paper feed roller for feeding a validation paper. In this conventional printer, as shown in FIGS. 19a and 19b of the accompanying drawings, a friction roller 69 is arranged in contact with the standard paper feed roller 68, and a validation paper feed roller 70 is arranged so as to move against and away from the paper feed roller 68. The standard paper P1 is fed as caught by the standard paper feed roller 68 and the friction roller 69. As to the validation paper P2, it is inserted between the standard paper feed roller 68 and the validation paper feed roller 70, whereupon the roller 70 is moved by a solenoid, etc., to press the validation paper P2 against the paper feed roller 68 for feeding.
In this conventional printer, if the validation paper P2 is set and fed when the standard paper P1 is set on the paper feed roller 68, the standard paper P1 is fed with the validation paper P2 since both the standard paper P1 and the validation paper P2 are caught by the standard paper feed roller 68 and the validation paper feed roller 70, resulting in waste of paper. Further, as the standard paper P1 is held between the paper feed roller 68 and the friction roller 69, the friction between the validation paper P2 and the standard paper P1 would be large to cause paper jamming.